Crankpin finishing apparatus

ABSTRACT

A FINISHING APPARATUS FOR A CRANKPIN ON A CRANKSHAFT INCLUDES A LATHE WHICH TURNS THE CRANKSHAFT WHILE THREE ANGULARLY SPACED FINISHING STONES CARRIED BY RACKS IN A MOVABLE HOUSING ENGAGE THE SURFACE OF THE CRANKPIN. GEAR TRAINS BETWEEN THE RACKS POSITIVELY COUPLE THE STONES TOGETHER FOR JOINT MOVEMENT AND MAINTAIN THEM AT AN EQUAL DISTANCE FROM A POINT FIXED IN RELATION TO THE HOUSING TO ROUND THE CRACKPIN WHILE FINISHING IT.

Feb. 16, 1971 R scHwAR 3,562,966

CRANKPIN FINISHING APPARATUS Filed July 15. 1968 3 Sheets-Sheet 1 INVENTOR, RUDOLF SCHWAR I 96ml 9'.

ATTORNEY Feb. 16, 1971 3 Sheets-Sheet 2 Filed July 15. 1968 FIG.2

INVENTOR, RUDOLF SCHW'AR ge To ATTORNEY Feb. 16, 1971 R. scHwAR CRANKPIN FINISHING APPARATUS Filed July 15. 1968 3 Sheets-Sheet 5 INVENTOR. scHw/3R RUDOLF ATTORNEY United States Patent 3,562,966 CRANKPIN FINISHING APPARATUS Rudolf Schwiir, Neviges, Germany, assignor to Maschinenfabrik Ernst Thielenhaus, Wuppertal-Barmen, Germany, a corporation of Germany Filed July 15, 1968, Ser. No. 745,025 Claims priority, application (grmany, July 15, 1967,

Int. Cl. B24b 9/02, 19/00 U.S. Cl. 51-347 9 Claims ABSTRACT OF THE DISCLOSURE My invention relates to an apparatus for surface grinding or finishing a bearing element and, more particularly, to an apparatus for grinding a crankpin on a crankshaft.

In order to microfinish or superfinish the hardened surfaces of the journals on crankpins, a grinding device of some kind is usually used in cooperation with a lathe that rotates a crankshaft. The grinding device is generally arranged in a housing that moves freely somewhat like a piston to follow the crankpin as the crankshaft is rotated. Often a simple band of abrasive paper or cloth is looped over the crankpin and held tightly so that, as the crankpin turns, it automatically grinds the crankpin surface or journal. According to another common method of grinding these crankpins, one or more small grinding stones are urged into contact with the surface of the crankpin by, for example, hydraulic pressure, springs, or simply gravity. These methods do not guarantee that the surfaces will be perfectly circular, nor are they capable of providing a circle of given diameter.

It is the object of my invention to provide an apparatus for the surface finishing of crankpins which not only enables microfinish or superfinish grinding, but also corrects irregularities of roundness of the crankpin.

This object is attained according to the main feature of my invention by grinding the crankpin with several, preferably at least three, finishing stones which are positively coupled together so that their grinding surfaces always lie on the circumference of a common circle whose center point is always at the same place in relation to the support or housing for the stones. This mechanism is used in cooperation with a turning mechanism (e.g. a lathe) and the grinding device itself is mounted to move with the crankpin as the crankshaft is rotated. With such an apparatus a projecting portion on an unround crankpin is quickly ground off while a depression on a crankpin is removed when the rest of the crankpin surface is ground down to its level. In both cases, the finishing tends to round the crankpin with respect to a well-defined point, something hitherto unattainable.

These three finishing stones are mounted on racks connected together by two gear trains and are angularly equispaced with an angle of 120 between them, as in a threejaw chuck. One of the racks is connected to a hydraulic servomotor that regulates the spacing of all three stones through the gear trains and drives the stones radially inwardly with positive force. The servomotor, which drives a threaded spindle, forms a positive drive analogous to a lathe leadscrew for advancing the stones independently of 3,562,966 Patented Feb. 16, 1971 the original contour of the crankpin. Joint retraction of all three stones allows a crankpin to be admitted into a slot in the jawlike housing and between the stones.

A plurality of these grinding or finishing devices can be provided to simultaneously finish all the journals on a crankshaft. Making the devices adjustable laterally and as to height makes it possible to use one grinding or finishing apparatus for crankshafts of varied dimensions.

The above and other objects, features and advantages will be more readily apparent from the following description, reference being made to the accompanying drawing, in which:

FIG. 1 is an elevational view of a grinding apparatus according to my invention;

FIG. 2 is a side view of a detail of the FIG. 1 apparatus; and

FIG. 3 is a section through a detail of the FIG. 1 apparatus, taken along line IIIIII of FIG. 1.

FIG. 1 shows a crankshaft 2 consisting of a plurality of crankpins 1 between webs 5. This crankshaft 2 is held by its ends 2a and 2b between a driving plate (faceplate) 3a in a headstock 4 and the dead center of a movable tailstock 3b of a lathe bed. Engaging two of these crankpins 1 are jaw-shaped supports or housings 6 which are carried between two guide plates 20 guided by means of frames 24 transfixed by pins 22 through a slot 21 (FIG. 2), the pins 22 being fixed in the plates 20 and slidable in the slot 21. These plates 20 are laterally slidable on rails 29 and 30 by means of carriages 19a and 19b. The lateral motion can be arrested by stop screws 19c. Up-anddown (vertical) motion of the plates 20 is controlled by lockable cross-slides 27 mounted on the upper slides 19a.

FIGS. 2 and 3 show the particular structure of the grinding device of my invention. Three finishing stones 7 are fitted into three holders 9 in turn fitted onto three coplanar racks 11, 12 and 13. The racks 11, 12 and 13 have bolts 9a passing longitudinally through them which threadedly engage in the rear of the holders and allow them to be replaced.

These three racks 11, 12 and 13 are fitted into slots in a center plate 8 held in the housing 6, and the lower two racks 12 and 13 lie alongside spacer bars 28, 28' which keep them aligned.

Between the upper rack 11 and the two lower racks 12 and 13 are two gear trains comprising coplanar sets of gear pairs 15-18 and 1518' mounted on pivots 15a- 18a and 15a'-18a. Thus, all three abrasive stones 7 are positively coupled together, movement of one stone necessitating movement of the two others whereby their grinding surfaces always define a circle having a center point that is fixed in relation to the housing 6.

The upper rack 11 is coupled through a U-shaped member 26 and a threaded spindle 25 movable in directions A and B to a hydraulic servomotor 14 connected through a conduit 14a to a control station not shown.

The ends 211 and 2b of the crankshaft 2 are connected between the plate 3a and the tailstock 3b, the latter being axially shiftable for properly receiving and clamping the end 211.

The plates 20 are slid laterally on the slides 19a and 1% until the housing 6 passes between the webs 5 defining the crankpin 1 to be finished, being then locked in place by the lockscrew 190. If necessary, the housing 6 can be adjusted for the proper up-and-down movement by means of a locking cross slide 27.

The servomotor 14 is subsequently actuated to pull the rod 25 and rack 11 in the radially outward direction A, thereby withdrawing all the stones 7. The housing 6 is manipulated to fit a mouth-like opening 10 over the crankpin 1, care being taken that the housing 6 does not brush against one of the webs 5 and is not canted when set. If this occurs, the slides 19a and 1% should be readjusted.

The motor 14 is now reversed to move the rod 25 and rack 11 in the inward direction B to bring the stones 7 into contact with the surface of the crankpin 1.

The drive 4 is started to slowly rotate the whole crankshaft 2 and thereby cause the crankpin 1 and the engaged stones 7 to move through a circle 23. Owing to its mounting on a single pin 22, the housing readily follows the motion of workpiece 1. As it rotates, the stones 7 grind the surface of the crankpin 1 and move constantly toward each other under the controlled pressure exerted on the rack 11 by the motor 14 until the desired amount of grinding is completed. By virtue of the positive coupling and triangular arrangement of the stones 7, any surface irregularities on the crankpin 1 are ground off, thus giving it an ideal circular shape.

To change the stones 7, one need only loosen the bolts 9a enough to free the holders 9 and then insert a new set. v

The improvement described and illustrated is believed to admit of many modifications within the ability of persons skilled in the art, all such modifications being con sidered within the spirit and scope of the invention except as limited by the appended claims.

I claim:

1. An apparatus for the surface finishing of a crankpin, said apparatus comprising:

means for rotating said pin about an axis parallel to said pin;

a support movable in a plane perpendicular to said axis; three pressure members movable for radial engagement with said pin and mounted on said support, at least one of said members being formed as a tool, said members being angularly spaced about said pin;

positive coupling means interconnecting said members for maintaining said members at identical distances from a common point fixed relative to said support; and

drive means for urging said members into contact with said pin, said coupling means comprising a respective rack carrying each of said members and at least 6. The apparatus defined in claim 1, further comprising means for shifting and locking said support along said axis.

7. The apparatus defined in claim 1 wherein said support includes two spaced, parallel plates, said members being mounted between said plates.

8. The apparatus defined in claim 7 wherein said plates are formed with an open-ended slot, said crankpin being receivable between said members in said slot, said means for rotating said crankpin being a lathe.

9. An apparatus for the surface finishing of a crankpin, said apparatus comprising:

means for rotating said pin about an axis parallel to said pin;

a support movable in a plane perpendicular to said axis;

three pressure members movable for radial engagement with said pin and mounted on said support, at least one of said members being formed as a tool, said members being angularly spaced about said p positive coupling means interconnecting said members for maintaining said members at identical distances from a common point fixed relative to said support; and

drive means for urging said members into contact with said pin, said support including two spaced, parallel plates, said members being mounted between said plates, said plates being formed with an open-ended slot, said crankpin being receivable between said members in said slot, said means for rotating said crankpin being a lathe.

References Cited UNITED STATES PATENTS 1,411,181 3/1922 Petersen et al 51-56 1,967,744 7/ 1934 Craft 51-241 2,138,258 11/1938 Sievers, Jr. 5-1-241 2,238,326 4/1941 Indge 51-348X 2,240,527 5/1941 Sunnen 51-55 2,309,615 1/1943 Sunnen 51-55 2,316,422 4/1943 Harris 51-349X 2,374,849 5/ 1945 Worley 51-351 3,456,391 7/1969 Venesia 51-55 FOREIGN PATENTS 573,713 4/ 1933 Germany.

OTHELL M. SIMPSON, Primary Examiner U.S. Cl. X.R. 

